Evaluating preservation and textural qualities of toast using guava and cabbage as fermentation substrate

• Main Authors: Liao, Po-Jung, 廖柏榮
• Other Authors: Yang, Huai-Wen
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/72336711774221056969

碩士 === 國立嘉義大學 === 食品科學系研究所 === 103 === Guava alone and combined with cabbage were employed as fermenting substrate for natural yeast using three guava/cabbage ratios: A=4/0, B=3/1 and C=2/2. The keeping quality and microbial count of the cultural solution (phase 1, P1) were investigated. The resulting P1 solutions were further incubated to stable yeast starter (phase 2, P2) adding flour and sugar. For phase 3 (P3), the cultures were mixed into dough; phase 4 (P4), proofed and baked into toasts. The expansion capabilities during P2 process, dough (P3) extensibility as well as textural and sensory characteristics of toasts (P4) were also evaluated. During P1, the solutions with addition of cabbage resulted in lower microbial count at the beginning, however, become higher comparing to ratio A. The storage of P1 would allow the microbial count to maintain at 105 cfu/ml for 15 days at preferable temperature of 4oC. The expansibility curves during P2 indicated a directly linear increase up to day 3, peaked at the 4th day (3.34±0.07 times), then become flat at 4oC, twice as large on 5th day and non-significant on the 10th day. As addition amount ratio C of cabbage increase, the resulted dough possessed a better extensibility. The textural profile of toast indicated that toasts made from commercially available CA yeast resulted in finer porous structure and lower hardness (439.09±102.92 g); whereas, those made from natural yeast possessed higher springiness of cohesiveness compared to CA yeast. As far as sensory evaluation is concerned, toast made from CA yeast scored the best texture (5.9/9) by the panelists. Attributed to densely distributed porous structure. Group B and C received a lower score (4.4/9) due to the formation of lactic acid that minimized the flavor and aroma of the toast. However, there were some panelists preferred the odor and hardness resulted from Group B and C. It would be concluded that the addition of cabbage to guava can expedite the fermentation process of natural mixed yeast substrates which would maintain a superior expansion capabilities with excess acidic flavor potentially beneficial for sourdough development.